Preoptic-hypothalamic periventricular lesions after food-associated drinking and circadian rhythms

For assessment of the effect of anteroventral third ventricle (AV3V) periventricular lesions on food-associated drinking, the free-feeding patterns of eating and drinking were continuously monitored before and after rats had undergone either AV3V lesions or control surgical procedures. Feeding and drinking were monitored with pellet-detecting eatometers and lick-detecting drinkometers. "Recovered" animals with AV3V lesions did not exhibit normal diurnal patterns of ingestion but consumed only half of their daily food and water during the dark portion of the day-night cycle. The strong temporal association between eating and drinking as well as a normal intrameal pattern of ingestion, i.e., minimal drinking within meals, was evident in animals with AV3V lesions. However, the significant positive correlation between meal size and meal-associated water intake characteristic of normal animals was absent in animals with AV3V lesions. These results suggest that the mechanism responsible for precise adjustment of water intake and meal size is disrupted by AV3V periventricular ablation. These findings indicate that AV3V periventricular tissue is critical for normal body-fluid homeostasis.